1. Field of the Invention
The present invention relates to an image analysis method, an image analysis program and a pixel evaluation system having the sames for evaluating an image display panel.
2. Description of the Related Art
Conventionally, there is a method for evaluating display by shooting a color liquid crystal panel with a CCD camera (Patent Document 1: Japanese Patent Laid-Open No. H8-327497). According to the Patent Document 1, when a color liquid crystal panel is shot with a CCD camera, a center coordinate, a leakage gray value in every pixel and a CCD element region covered with a pixel image are saved firstly. Then a white raster is formed on a color liquid crystal display panel to be examined and shot with a CCD camera. Correction processing is carried out for removing the leakage gray value from outputting in every pixel displayed to a sensor element surface of a CCD camera. Then, output of the sensor element covered with the pixel image is added as well as obtaining a correction gray scale and a correction gray scale in every pixel is obtained. The liquid crystal display surface is reconstructed from a center coordinate and a correction gray value in every pixel and a liquid crystal display image is expressed by binary with a threshold; and thus, a defect is detected.
When a digital camera with the use of CCD which has not much high resolution for a panel is employed to reduce the cost of a digital camera as typified by a CCD camera with the use of a CCD type sensor, a pixel pitch of a digital camera shifts to a pitch of a non-display area such as a black matrix existing between each pixel, of the panel; accordingly, moire (indicates a stripe design which does not exists under normal condition) is generated more intensively. And thus, display unevenness which is to be essentially evaluated becomes difficult to be distinguished. Especially, moire has significant effects on using a panel having low aperture ratio of a pixel. In addition, in the case where a shot image is displayed in a reduced-size on a display or printed in a reduced-size with a printer, moire appears more intensively since there are also influences of a pixel of the display and a dot of the printer.
To reduce the influences of moire, it is required to reconstruct an image by recognizing a center coordinate of each pixel with respect to a shot image with a digital camera with high accuracy and by calculating an average luminance value in each pixel unit. Note that a specific method for recognizing the pixel position of a panel is not mentioned in the description of evaluation equipment disclosed in the above Patent Document 1.
Alternatively, as a method for relieving moire, there is a method of blurring by defocusing when shooting with a digital camera or blurring a shot image using a software; however, a display defect portion such as a point defect is blurred and hard to distinguish since it is required to be blurred much intensively. Besides, display unevenness which is to be essentially evaluated is observed differently from the actual display unevenness.
Further alternatively, as a method for relieving moire, it is considered that there is a method of sufficiently increasing the number of pixels of a digital camera with respect to the number of pixels of a panel. However, it is difficult to manufacture a high-definition digital camera which has higher resolution than that of a high-resolution panel without lowering a dynamic range; and thus, it is required to employ a very expensive digital camera. Therefore, a method for relatively increasing pixel density of a digital camera by enlarging a part of a panel display surface and shooting at several times is employed. However, in this case, it takes extra effort and time to shoot, and besides, the size or cost of evaluation equipment increases when combined with an automatic stage. In addition, it takes long time to analyze various kinds of data after shooting since the size of image data after shooting is also greatly enlarged. Furthermore, even saving evaluation data takes time and consumes an enormous storage capacity of a recording medium.